There has been an increase in the need or desire to know or find the location of objects such as cell phones, keys, tablets, and other electronic devices. A common solution to this problem is to have the device transmit a continuous wave tone. When measured at two or more antennas, the tone allows for measurement of phase difference between the two antennas to determine the angle of arrival. This allows the device to be located.
A major problem is that the devices in question typically lack the hardware capability to transmit a continuous wave tone. While there are suggestions of modifying some communications standards, such as Bluetooth or Bluetooth Low Energy (BLE), to allow for the transmittal of continuous wave tones, this will require hardware and software upgrades. In many cases, continuous wave tone signals also violate Federal Communications Commission rules and regulations.
Further, in the case of Bluetooth and BLE, the signals make use of frequency modulation (FM) transmission, which have unpredictable phase. The signals are also whitened using a pseudo random pattern to help control the spectrum of the signal. While effectively spreading the signal spectrum, this also randomizes the phase of the transmitted signal. The combination of these features makes it very difficult to find the phase difference of the signal by simply measuring with multiple antennas. Simple phase difference routines lack the accuracy to determine the location of a device. There is a need for a method or system that can determine the location of a device using existing hardware in the device and existing communications protocols, such as Bluetooth or BLE.
The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced.